The present invention relates generally to electronic devices having a circuit module which is covered by a layer of silicon gel for environmental protection, and more particularly relates to a mass flow air sensor utilized to measure the air intake of an automobile engine and the protection of the sensor""s circuit module.
The prior art teaches the importance of measuring air intake into an internal combustion engine for purposes of improving engine control. One type of mass flow air sensor includes a housing that projects into the main air intake tube of the engine for sampling the intake air and generating a signal representative of the instantaneous mass fluid flow through the passage. The housing defines a circuit chamber having a circuit module positioned therein. The circuit module includes various electronic components and wire bonds linked to those components for generating the air flow signal that is sent to the electronic engine control system. Typically, the circuit module is covered by a silicon gel layer to protect the circuit module from the environment. Finally, the circuit chamber is closed by a housing cover.
It has been found that the silicon gel layer in the circuit chamber shows large motions or vibrations which are induced by vehicle vibration. Unfortunately, these large vibrations or motions in the silicon gel can cause premature fracturing of the circuit components or wire bonds. Accordingly, there exists a need to provide a sensor having an electronic component that is well protected from the environment, provides good heat transfer, and which can withstand the vibrations on the sensor from the automobile environment.
The present invention provides a slosh suppressor for preventing damage to electronic components and the wire bonds contained inside the housing of an electronic device such as a sensor, and most preferably a mass air flow sensor. Generally, the slosh suppressor is formed into a sensor module comprising a sensor housing defining a circuit chamber. A circuit module is positioned within the circuit chamber and has a silicon gel layer positioned thereon for protecting the circuit module from the environment. A housing cover is structured to engage the sensor housing and close the circuit chamber. The housing cover has a projection extending into the circuit chamber and engaging the silicon gel layer to reduce vibrational displacement of the silicon gel layer and protect the circuit module.
The projection extends into the silicon gel layer, and preferably extends only partially into the silicon gel layer. The projection divides the silicon gel layer into multiple sections and inhibits the transfer of vibrational energy between sections of the silicon gel layer. The separation of the silicon gel layer into separate mass sections increases a resonant frequency in each section and reduces the movement of the silicon gel layer when the sensor module is subject to vibration.
Preferably, the housing cover includes a plurality of projections extending into the circuit chamber and engaging the silicon gel layer to reduce vibrational displacement. Preferably the plurality of projections do not intersect or otherwise are arranged to prevent trapped air within the circuit chamber between the silicon gel layer and the housing cover. Most preferably, the projections are positioned adjacent the wire bonds and the electronic components to provide small mass sections of silicon gel layer proximate the wire bonds. The smaller the mass section, the higher the resonant frequency giving smaller motions in the mass section. Finally, the housing cover may include a plurality of fins on its outer surface which promote heat transfer from the circuit module through the cover.